Capaea nemoralis is a terrestrial creature of the mollusca family, chosen for study due to its sedentary nature, 20m in a generation, and its diverse polymorphic traits. The use of this snail species, as opposed to humans, is due primarily to their visual display of their phenotype on their shells. This allows for the identification of phenotype both pre and post death. This lack of movement also leads to sub-populations in geographically close proximity displaying a variety of phenotypes. This means that we will be able to identify if selection is a more powerful force than genetic drift depending on phenotypes present in various terrains. Method
We shall be conducting a horizontal line transect across a consistent altitude as this eliminates the confounding variables associated with altitude differences: temperature, wind exposure and humidity. We are sampling across 6 sites over 3 different habitats along the line transect. The allocation of these sites will be stratified as to equally distribute 2 sampling sites to each habitat. The consistent distribution of sampling sites is due to a need for independence of samples in order to go some way towards eradicating the effects gene flow upon selection. Advantages One advantage of the method we are using is its control of confounding variables. By controlling height we are controlling humidity, temperature, moisture and wind exposure. This will lead to a greater ecological validity in our results, and due to the strict control of variables, a greater degree of replication. Disadvantages Due to time and economical constraints we are limited to taking 6 samples at a single small site in England. This may mean that our sub-populations are actually part of the same population and gene flow occurs regularly between these. If this is the case, then we would not see any indication of habitats effect on selection.
Stephanie Chan*
Stuttee Mehra
Kishan Patel
Arran Hamlet
Lauren Tithecott
Introduction
Capaea nemoralis is a terrestrial creature of the mollusca family, chosen for study due to its sedentary nature, 20m in a generation, and its diverse polymorphic traits.
The use of this snail species, as opposed to humans, is due primarily to their visual display of their phenotype on their shells. This allows for the identification of phenotype both pre and post death. This lack of movement also leads to sub-populations in geographically close proximity displaying a variety of phenotypes.
This means that we will be able to identify if selection is a more powerful force than genetic drift depending on phenotypes present in various terrains.
Method
We shall be conducting a horizontal line transect across a consistent altitude as this eliminates the confounding variables associated with altitude differences: temperature, wind exposure and humidity.
We are sampling across 6 sites over 3 different habitats along the line transect. The allocation of these sites will be stratified as to equally distribute 2 sampling sites to each habitat. The consistent distribution of sampling sites is due to a need for independence of samples in order to go some way towards eradicating the effects gene flow upon selection.
Advantages
One advantage of the method we are using is its control of confounding variables. By controlling height we are controlling humidity, temperature, moisture and wind exposure. This will lead to a greater ecological validity in our results, and due to the strict control of variables, a greater degree of replication.
Disadvantages
Due to time and economical constraints we are limited to taking 6 samples at a single small site in England. This may mean that our sub-populations are actually part of the same population and gene flow occurs regularly between these. If this is the case, then we would not see any indication of habitats effect on selection.